Dear Sir. Concerning your issue about the formulas for GSI estimation. The A scale is defined by 1.5 JCond89 while the B scale is defined as RQD/2. The value of GSI is given by the sum of these scales which results in the relationship:

GSI = 1.5 JCond89 + RQD/2

I think the following below links may help you in your analysis:

https://rocscience.com/documents/hoek/references/Quantification-GSI-Chart-Hoek-Carter-Diederichs.pdf

http://www.geoplanning.it/test/wp-content/uploads/2012/02/GSI.pdf

https://arxiv.org/ftp/arxiv/papers/1210/1210.3024.pdf

https://pdfs.semanticscholar.org/d1f6/6702cacf65f96470cf87efe137042d24b4e6.pdf

Thanks

thank you very much sir.

Hi Rafik,

1. The first formula you have shown should be written as (see Hoek and Brown 1997):

GSI = RMR'89 - 5 (for GSI>=18 or RMR>=23)

where RMR'89 = P1+P2+P3+P4+15+0 (evaluation for groundwater = 15 and for joint adjusment = 0)

(GSI = 9log [(RQD / Jn) (Jr / Ja)] + 44) is valid for GSI

Hi dear Erion,

Very clear,

Thanks a lot

Rafik

GSI = RMRbasic-5.......... this eq is valid when GSI>25.

GSI = 9log [(RQD / Jn) (Jr / Ja)] + 44 is old eq given by hoek 1995, there is some correction, the eq is GSI = 9ln [(RQD / Jn) (Jr / Ja)] + 44